1. Field of the Invention
The present invention relates to an electronic throttle control system that performs initialization of memory that stores failure information relating to electronic control of a throttle valve at a predetermined timing.
2. Description of the Related Art
Conventionally, when a mode switch on an electronic control unit (ECU) is set to OFF, normal engine control is performed for controlling a throttle opening according to an operational state. When an ON mode switch setting is detected, the throttle opening is controlled to drive a throttle actuator so that a specific operation pattern suited to diagnosing failure is performed, thus performing self-diagnosis for detecting system abnormalities. Failure diagnosis can thus be performed swiftly and accurately, without the diagnosis being stopped during the vehicle check because the throttle opening changes due to an accelerator operation mistake by an operator, causing deviation from the specific operation pattern. The vehicle checking efficiency can thus increase (for example, refer to JP 11-82133 A (page 1, FIG. 1)).
The conventional system described above eliminates operational mistakes made by the operator by automatically producing a specific operation pattern (throttle valve control pattern) for failure diagnosis. Operational mistakes can be eliminated because there is no accelerator operation by the operator when this type of system is used. However, failure of the throttle valve and the like developing during the specific operation pattern of the vehicle has not been considered.
Further, throttle valve failure and throttle position sensor failure are detected with conventional electronic throttle valve control. When these types of failure are detected, the throttle valve control is stopped in order to ensure vehicle reliability, and failsafe control, such as fixing the throttle valve opening to a predetermined position, is performed.
This failsafe control continues until an electric power source for an ECU is turned off. Information in order for the failsafe control to continue, and information on a failure location that has caused the failsafe control to be performed, are stored in a memory as failure information relating to the throttle valve electronic control.
However, there are cases where it becomes necessary to initialize the memory that stores the failure information after repairing the detected failure location, during verification by performing failure detection again while the vehicle ignition is on, and the like. The ECU therefore has a function whereby it is possible to initialize the memory that stores the failure information by using a tool that is connected from an external portion.
There are also cases where initialization of the memory that stores the failure information is performed when a failure mode develops that leads to a state in which the throttle valve opens more than necessary, after which failure detection is performed, and the vehicle is operated in a state where the vehicle reliability is maintained by the failsafe control.
However, there is a problem when the vehicle is operated in a state where the vehicle reliability is maintained by this type of failsafe control. Once the memory that stores the failure information relating to the throttle valve electronic control is initialized, a state again results where the throttle valve opens more than necessary.